In the beloved American stories of the Little House on the Prairie, author Laura Ingalls Wilder writes emotionally about how scarlet fever robs her big sister Mary of her sight.

But in a new study published today in the journal Pediatrics, University of Michigan researchers found it is likely scarlet fever had nothing to do with Mary's blindness.

Senior author Beth A. Tarini, M.D., and her co-authors used evidence from newspaper reports, Laura Ingalls' memories and school registries to conclude Mary's blindness was probably caused by viral meningoencephalitis.

"Since I was in medical school, I had wondered about whether scarlet fever could cause blindness because I always remembered Mary's blindness from reading the Little House stories and knew that scarlet fever was once a deadly disease," says Tarini, an assistant professor of pediatrics in the Child Health Evaluation and Research Unit at the University of Michigan's C.S. Mott Children's Hospital.

"I would ask other doctors, but no one could give me a definitive answer, so I started researching it."

Mary Ingalls went blind in 1879 at age 14. Tarini and her co-authors found evidence in Laura Ingalls Wilder's memoirs and letters that described Mary's illness as "spinal sickness" with symptoms suggestive of a stroke.

The study quotes a local newspaper item that reports that Miss Mary Ingalls was confined to her bed and "it was feared that hemorrhage of the brain had set in (sic) one side of her face became partially paralyzed."

"Meningoencephalitis could explain Mary's symptoms, including the inflammation of the facial nerve that left the side of her face temporarily paralyzed," Tarini says, "and it could also lead to inflammation of the optic nerve that would result in a slow and progressive loss of sight."